1. Field of the Invention
The present invention relates to an apparatus and method for the treatment of anaerobic bodies of water and, more particularly, to an apparatus and method for treatment of agricultural waste such as may be found in an anaerobic waste lagoon.
2. Description of the Background Art
Over the past decades there has been a shift from smaller localized family farms toward larger integrated confinement agricultural operations. Specifically, large agricultural operations referred to as concentrated animal feeding operations (CAFO""s) may utilize confinement barns to house a large number of livestock such as swine, poultry or dairy cows. Using the swine industry as an example, often numerous hog-confinement operations are grouped in close proximity forming xe2x80x9cmega-farmsxe2x80x9d which may house tens of thousands of hogs. Similarly, the dairy industry operates using large factory farms that house thousands of animals in a relatively small land area. While these larger agricultural operations have numerous advantages, attendant with these larger facilities are pollution problems relating to the handling and treatment of manure and wastewater (hereinafter collectively xe2x80x9cwastewaterxe2x80x9d). By way of example, pollution problems associated with liquid animal waste, such as produced by the swine industry, include nitrogen, phosphorus, solids, bacteria and foul odors that result from anaerobic digestion. Environmental concerns more specifically center on odor and ground and surface water quality issues and impacts.
Traditionally, animal wastes and wastewater therefor is collected and stored in waste treatment lagoons or waste storage ponds where it undergoes minimal treatment. Most agricultural facilities use anaerobic digestion for treatment of animal wastes and wastewater. The primary reasons for using anaerobic digestion is simplicity and cost. Wastewater is simply discharged from the animal storage facility into an open lagoon or plurality of lagoons (ponds used to store and treat thousands to millions of gallons of animal waste) where the waste undergoes natural anaerobic digestion. After retention in the lagoon system, wastewater is usually land applied via spray irrigation. However, over forty (40) noxious gases may be emitted from anaerobic lagoons at hog and/or dairy farms including ammonia, methane and hydrogen sulfide. Additionally, the time required for digestion of the organic wastes is relatively long, from weeks to months. Some current regulations require a minimum residence time of 180 days for animal waste facilities using anaerobic lagoons for digestion. Neighbors find odors emanating from lagoons, confinement houses, and fields onto which wastes are sprayed to be a nuisance. In fact, as a result of odor problems associated with anaerobic lagoons, certain states have legally mandated buffer zones or designated land areas between lagoon sites and populated areas.
Oftentimes, the reduction of organics and nutrients within an anaerobic lagoon is minimal and therefore high quantities of nitrogen, phosphorus, etc., are applied to the land during spray irrigation. These nutrients readily build up high residual concentrations in the soil, leach directly into the groundwater, or run-off into surface waters causing algal blooms, oxygen deficiencies and fish kills.
New studies have also shown that lagoons are leaking and there have been pollution problems with the groundwater, rivers, lakes and coastal waters primarily in states where the high concentrations of hog or other farms are located. Another problem attendant with traditional anaerobic settling lagoons is that occasionally the water overflows the lagoons or the earthen containment berms collapse, primarily during periods of heavy rainfall, and the wastewater runs off into streams, rivers and lakes, causing severe pollution problems. When wastewater escapes from these lagoons, either resulting from overflows or other failures, the high concentration of pollutants has adverse effects on the receiving waters and commonly results in groundwater contamination and massive fish and other aquatic life kills.
The most critical problem in the recent past has been with the microorganism Pfiesteria piscicida. Pfiesteria piscicida is a dinoflagellate related to the species of dinoflagellates that cause xe2x80x9cred tidesxe2x80x9d. This bacterium has the ability to take on up to twenty four (24) different forms during its life cycle and can attack and kill fish within hours. Recent outbreaks of Pfiesteria piscicida could be attributed to the increase in nutrients in the water or to the weakening of the fish due to stress caused by lack of oxygen and/or elevated ammonium levels, among other factors.
By way of example, hog anaerobic lagoon liquid effluent has nutrient characteristics including high levels of biochemical oxygen demand (BOD5), Total Nitrogen (TN) and Phosphorus that cannot be decreased to acceptable levels by anaerobic treatment alone.
Even with bacterial digestion within an anaerobic lagoon, significant amounts of sludge accumulate in an anaerobic lagoon. Anaerobic lagoons commonly fill to capacity fairly quickly which displaces the designed retention capacity of the lagoon in a short period of time. Anaerobically digested sludge is not suitable for commercial use or land application at typical loading rates in the anaerobically digested state.
Hogs produce two to four times as much waste, per hog, as the average human and, in North Carolina alone, hogs produce about 9.5 million tons of manure a year. Additionally, dairy cows produce up to twenty times as much waste, per cow, as the average human. Therefore, a great deal of land is required for spreading the highly concentrated waste since often no discharge is permitted from animal waste facilities. Farmers who specialize in raising large quantities of animals are forced by regulations to use larger and larger areas of land in which to spread the large quantities of wastes generated from higher numbers of animals. This has, and will continue, a trend toward having to sacrifice more land to simply dispose of the waste. The land utilized for land spreading of waste cannot be just any land, but must be carefully selected or altered so as to prevent any rainfall runoff discharging into any surface waters. The land must be planted with species capable of tolerating high nitrogen and high phosphorus containing wastes. The farming industry is running out of places to spread or spray the waste from lagoons.
While efforts are being made to regulate new farm facility construction, abandoned waste lagoons are still prevalent. By way of example, North Carolina has an estimated seven hundred abandoned lagoons.
Continuing efforts are being made to improve agricultural and animal waste treatment methods and apparatus. By way of example, note U.S. Pat. No. 5,472,472 to Northrop and U.S. Pat. No. 5,078,882 to Northrop. U.S. Pat. No. 5,472,472, discloses a process for the transformation of animal waste wherein solids are precipitated in a solids reactor, the treated slurry is passed to a bioreactor zone where soluble phosphorus is precipitated with metallic salts, the slurry is aerobically and anaerobically treated to form an active biomass. The aqueous slurry containing bioconverted phosphorus is passed into a polishing ecoreactor zone wherein at least a portion of the slurry is converted to a beneficial humus material. In operation, the system requires numerous chemical feeds and a series of wetland cells comprising microorganisms, animals and plants. See also U.S. Pat. Nos. 4,348,285 and 4,432,869 to Groeneweg et al.; U.S. Pat. No. 5,627,069 to Powlen; U.S. Pat. No. 5,135,659 to Wartanessian; and U.S. Pat. No. 5,200,082 to Olsen et al. (relating to pesticide residues); U.S. Pat. No. 5,470,476 to Taboga; and U.S. Pat. No. 5,545,560 to Chang.
Another grouping of background patents are those which disclose methods of treating wastewater rich in nutrients. Note U.S. Pat. No. 5,626,644 to Northrop; U.S. Pat. No. 4,721,569 to Northrop; and U.S. Pat. No. 4,183,807 to Yoshizawa et al.
Another grouping of background patents are those which disclose methods of producing humus material or spreadable fertilizer from animal waste. By way of example see U.S. Pat. No. 5,538,529 to Northrop; U.S. Pat. No. 5,525,239 to Duske; and U.S. Pat. No. 5,282,879 to Baccarani.
The disclosures of the documents submitted as part of the Information Disclosure Statements previously filed with U.S. application Ser. No. 09/250,828 and U.S. application Ser. No. 09/167,275 are incorporated by reference in their entirety.
Not withstanding the existence of such prior art treatment systems, it remains clear there is a need for a method and apparatus for the treatment of anaerobic bodies of water that can be utilized to treat animal waste lagoons in an economical and environmentally friendly fashion.
Efforts to improve the methods and apparatus to treat anaerobic bodies of water, specifically animal waste treatment lagoons, continues. Accordingly, it is an object of the present invention to provide an improvement that overcomes inadequacies of the prior art method and apparatus and provides an improvement, which is a significant contribution to the advancement of the art.
Another object of this invention is to provide a new and improved system for treatment of anaerobic bodies of waste and wastewater that has all the advantages and none of the disadvantages of the prior art.
A further object of the present invention is to provide a system to treat animal waste lagoons having a minimal impact on the environment.
Another object of the invention is to provide an approved treatment apparatus and method that significantly reduces the amount of nutrient loading in the treated anaerobic water.
Another object of the invention is to provide an apparatus and method of treating agricultural wastewater whereby minimal or no land application is required.
Another object of the invention is to provide an effective treatment of the wastewater using methods that will greatly reduce, if not eliminate, the foul odors associated with anaerobic lagoons.
Another object of the invention is to treat wastewater without greatly reducing the nutrients present in any recovered sludge.
Another object of the invention is to provide a system for the purification of agricultural wastewater that is economically feasible.
Another object of the invention is to provide an apparatus and method for treatment of agricultural waste, which meets regulatory compliance.
Another object of the invention is to provide a nutrient rich organic fertilizer as a by-product of the treatment apparatus and method of the present invention.
Another object of the invention is to enable the conversion of an anaerobic wastewater lagoon to a freshwater pond.
The foregoing has outlined some of the pertinent objects of the invention. These objects should be construed to merely be illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.
For the purposes of summarizing the invention, the present invention is drawn to a unique apparatus and method for treating anaerobic bodies of water or an isolated body of wastewater including, but not limited to, agricultural waste treatment lagoons. Hereinafter, the term xe2x80x9cwastewaterxe2x80x9d will be used to refer to either agricultural waste or organic rich water that may be subject to treatment utilizing the apparatus and method of the present invention and any constituent sludge. The apparatus and method of the present invention may be readily sized and configured depending upon the amount and constituents of the wastewater and sludge to be treated. In a preferred embodiment, typical of that which may be utilized to treat an existing animal wastewater treatment lagoon, the apparatus and treatment method of the present invention will consist of several phases once the parameters of the wastewater have been ascertained. First, specially selected bacteria are cultivated based upon the wastewater parameters. This specialized bacteria is then utilized in bio-augmentation of the wastewater lagoon. Specifically, bacteria will be isolated and propagated specific for the wastewater and once introduced, will create a selective dominance within the lagoon and enhance digestion of the waste. The wastewater lagoon is equipped with an aeration means and mixing means such that the wastewater undergoes aerobic digestion utilizing the specially selected bacteria. Both the water and sludge are mixed and aerated while the added bacteria, cultured specifically to digest the constituents particular to the body of water, speed up the treatment. The aerobic treatment in the lagoon serves to break down organics and oxidize both macro- and micro-nutrients resulting in the reduction of BOD5, COD, TKN, and ammonium-nitrogen. Preferably the lagoon incorporates an energy efficient aeration/circulation system to promote mixing and oxygenation.
The solids separation or clarification phase preferably occurs in the existing animal wastewater treatment lagoon. However, if the wastewater treatment lagoon is large or there is a significant amount of solids, in a second embodiment aerobically treated wastewater may be removed and clarification may occur in aboveground tanks. As used herein, solids separation or xe2x80x9cclarificationxe2x80x9d will refer broadly to flocculation, coagulation and sedimentation. The clarification process will be facilitated through the addition of polymer.
Depending upon the size of the anaerobic body of water, digested sludge that has undergone aerobic treatment and clarification may then undergo dewatering. Since it is an aerobic not anaerobic sludge, odor should be greatly reduced or eliminated. The nutrient rich accumulated dewatered sludge may be deactivated for use as solid fertilizer while the resultant water is capable of supporting an ecosystem.
In an alternative or third embodiment, the foregoing methodology may be applied towards anaerobic bodies of water such as may be found in a dead-end canal. Specifically, navigable waterways such as canals, creeks, streams and even rivers, at times must undergo periodic dredging due to the build up of sludge and silt. The sludge and silt build up is typically due to the accumulation of organic material and the consistency varies from one location to the other. In the third embodiment, specially propagated bacteria are added to the sludge prior at any dredging operation occurring. The area to be dredged may be isolated, aerated and mixed to support the aerobic bacteria. After testing to determine that organics have been removed, the aerobic sludge will then be pumped from the dredge site where it will undergo clarification with the resulting removed sludge being transported to a disposal location. The resultant clarified water would be removed to the spoil area.
By utilizing the apparatus and method of the present invention, small bodies of water, ie. anaerobic animal waste treatment lagoons, can be treated in situ with aeration, bacteria and mixing of the sludge. After the mixing and aerobic digestion process using specialized bacteria, the sludge then undergoes solids separation/clarification using a polymer with the sludge being either removed and dewatered or left in place. If removed, the material is suitable for use as a soil enhancer or organic fertilizer. If left in place, the sludge becomes a source of nutrients to support plant growth and the development of an aquatic ecosystem. Large bodies of water can be treated by the removal of the untreated sludge and providing aerobic treatment in a separate vessel. After this treatment, the clarified liquid is returned to the body of water while the treated sludge is allowed to undergo the digestion process and then is dewatered for further processing and use.
The foregoing has outlined rather broadly the more pertinent and important features of the present invention. The detailed description of the invention that follows is offered so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the disclosed specific embodiment may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent construction does not depart from the spirit and scope of the invention as set forth in the appended claims.